Continued advances in the design of electronic devices for data processing and communications systems is placing rigorous demands on electrical connectors. Specifically, electrical connectors providing greater density and isolation for signal transmission are needed for design advances which increase integration of solid state devices and which increase the speed of data processing and communication. Designing connectors to have higher degrees of isolation requires careful consideration of the problems which result from decreasing the distance between contacts in order to increase density. Primarily, as the distance between contacts decreases, the likelihood of undesirable electrical cross talk between contacts increases.
As more functions become integrated on semiconductor chips or on flexible circuit substrates and more chips are provided on printed circuit boards (PCBs), each PCB or flexible circuit must provide more inputs and outputs (I/Os). The demand for more I/Os directly translates to a demand for greater density. In addition, many system components are capable of operation at faster speeds than previously. Faster speed can result in the generation of potentially interfering signals, i.e., signals which can cause crosstalk and noise. The connectors used in such high-speed board-to-board, board-to-cable and cable-to-cable communications may be treated for design purposes like transmission lines in which crosstalk and noise become significant concerns. Indeed, the electrical performance of high-speed board-to-board, board-to-cable and cable-to-cable communications is dependent upon the amount of crosstalk and noise introduced at the connector interface.
As was recognized in U.S. Pat. No. 4,824,383--Lemke, incorporated herein by reference, an important connector design consideration is the provision of an electrical connection while avoiding degradation of component performance. Prior to this patent, connector designs had been proposed in which a ground plane and alternating ground contacts together with shielding extensions were introduced to minimize electrical discontinuities, i.e., crosstalk and noise. While performance was controlled in such prior devices, density was limited.
U.S. Pat. No. 4,824,383 proposed designs for plug and receptacle connectors for multiple conductor cables or multiple trace substrates. In such designs individual contact elements or groups of contact elements were electrically isolated to prevent or minimize crosstalk and signal degradation. In the individually isolated design, a conductive base plate was provided with a number of walls arranged in side-by-side relationship, thereby defining a number of channels. A contact support member formed from electrical insulating material was designed to have a number of fingers, wherein a finger was positioned within each channel. Each finger of the contact support member supported an individual contact element.
Although, the connectors disclosed in U.S. Pat. No. 4,824,383 increased contact element density, industry driven density demands continued to grow. U.S. Pat. No. 5,057,028--Lemkeetal. and U.S. Pat. No. 5,169,324--Lemke et al. (now U.S. Pat. No. Re. 35.508), all incorporated herein by reference, disclose two row plug and receptacle connectors for attachment to printed circuit boards (PCBs), so that when such connectors are mated the PCBs are electrically interconnected. Although, these plug and receptacle systems provide higher contact density, electrical isolation is provided primarily between sets of contacts rather than between individual contacts.
In an attempt to provide isolation between individual contacts, various design schemes have been proposed. These design schemes can be generally catagorized as a coaxial structure (a single contact surrounded by a conductor), as a twinax structure (dual contacts surrounded by a conductor), as a microstrip structure (a number of contacts provided on one side of a single ground plane), and as a stripline structure (a number of contacts sandwiched between two ground planes.
U.S. Pat. Nos. 4,846,727, 5,046,960, 5,066,236, 5,104,341, 5,496,183, 5,342,211 and 5,286,212 disclose various forms of stripline structures incorporated into a plug and receptacle system. Generally, however, these systems can be described as providing columns of contact elements having conductive plates disposed between each column. The connectors are designed so that the plug and receptacle ground plates contact one another. A further aspect of this system is the modular design of the receptacle. Each row of receptacle contact elements are molded into a frame of dielectric material. The overall receptacle assembly, thus includes, a housing to which the ground plates and dielectric frames are attached in alternating layers. Outer shields are also disclosed for surrounding the receptacle exterior. One of the problems of this system, however, is that while density is increased, for certain applications, density is still insufficient. However, for some applications, it is necessary for each transmission contact element to be individually isolated.
The present invention concerns, in part, the design of a module which when combined with other modules provides a series of conductive chambers or pockets. A transmission contact element is positioned within each pocket. It is recognized that individual isolation, i.e., a coaxial isolation approach, is not new. Indeed such arrangements are disclosed in U.S. Pat. Nos. 4,571,014 and 5,620,340.
One of the problems with such connector systems is that the contact element density remains insufficient for certain applications. Consequently, a need still exists for a connector system which maximizes the number of individually isolated contact elements.